A powder metallurgy method for improving strength and obtaining cohesive microstructure

Abstract

The present invention is a powder metallurgy method for improving strength and obtaining a cohesive microstructure. The metallurgical method first causes metal powder or metal droplets to undergo plastic deformation under the action of mechanical stress and low-temperature cooling. The plastic deformation is then retained without recovery or recrystallization. The product of the metal powder or metal droplets after the above treatment and cooling is layered and stacked, and then hot-pressed and sintered. After cooling, a cohesive microstructure material can be obtained. The device for achieving mechanical stress and low-temperature cooling in the metallurgical method comprises a cooling plate (1), a cooling jacket (2) and a hot pressing chamber (3). The cooling plate (1) can rotate around its central axis and has fan-shaped blades installed at its edge. A cooling jacket (2) containing liquid nitrogen is arranged around the cooling plate (1), and a hot pressing chamber (3) is arranged below the cooling jacket (2). The method makes each component exhibit anisotropy through the sequential design of powder layering, so that the material achieves higher strength along a specific direction.

Description

Technical Field

[0001] The invention relates to a powder metallurgy method for improving strength and obtaining a cohesive microstructure, and belongs to the technical field of heat dissipation component processing and manufacturing. Background Art

[0002] TiAl-based powder metallurgy bulk materials are widely used in the manufacture of components in the aerospace field due to their mechanical properties such as high strength. However, this material is brittle and easily damaged. Therefore, how to improve the toughness and improve the brittleness of TiAl-based powder metallurgy bulk materials has become a hot topic for researchers. At present, a series of manufacturing methods are being explored at home and abroad, usually by incorporating other toughening phases to improve their brittleness. However, these methods often require the prefabrication of many alloy phases, and the adjustment method is not flexible. In addition, the study found that the alloy phase strengthening changes under stress and high temperature conditions. The reason for the failure of the alloy under long-term heating loading conditions is that the strengthening elements in the alloy that resist dislocations are greatly reduced. Summary of the Invention

[0003] The present invention is designed to address the above-mentioned existing technical situation and provides a powder metallurgy method for improving strength and obtaining a cohesive microstructure. This method makes each component exhibit anisotropy through the sequential design of powder layering, so that the material can achieve higher strength along a specific direction.

[0004] The object of the present invention is achieved through the following technical solutions:

[0005] This powder metallurgy method for improving strength and obtaining a cohesive microstructure first causes metal powder or metal droplets to undergo plastic deformation under the action of mechanical force and low-temperature cooling. The plastic deformation will then be retained without recovery or recrystallization. The product of the metal powder or metal droplets after the above treatment and cooling is layered and stacked, and then hot-pressed and sintered. After cooling, a cohesive microstructure material can be obtained.

[0006] During implementation, the device for achieving mechanical stress and low-temperature cooling in the metallurgical method includes a cooling plate 1, a cooling jacket 2 and a hot pressing chamber 3. The cooling plate 1 can rotate around its central axis and has fan-shaped blades installed on the edge. A cooling jacket 2 with liquid nitrogen inside is arranged around the cooling plate 1, and a hot pressing chamber 3 is arranged below the cooling jacket 2.

[0007] In addition, the fan-shaped blades are distributed along the radial direction of the rotation circumference of the cooling disk 1 .

[0008] In addition, the cooling jacket 2 and the hot pressing chamber 3 are made of stainless steel.

[0009] During implementation, the steps of preparing the Mg-Al-Ti-Cu compound using the device are as follows:

[0010] Step 1: Prepare Mg powder, Al powder, Ti powder and Cu powder with a particle size of -300 to -400 mesh, wherein the volume percentages of Mg powder and Cu powder are 20% and 10% respectively, and the volume percentages of Ti powder and Al powder are both 35%;

[0011] Step 2: Start the cooling plate 1 and rotate it at a speed of 50-200 rad / s. Sprinkle Ti powder from the top of the cooling plate 1, allowing the Ti powder to pass through the cooling plate 1 and the cooling chamber 2 into the hot pressing chamber 3 to form a layer. During this process, the Ti powder is hit by the fan-shaped blades of the cooling plate 1 and collides with the inner wall of the cooling chamber 2, causing plastic deformation. However, due to the cooling effect of the liquid nitrogen in the cooling jacket 2, recovery and recrystallization do not occur.

[0012] Step 3: The molten Al powder droplets are passed through the cooling plate 1 and the cooling chamber 2 into the hot pressing chamber 3 to form a layer. During this process, the aluminum powder droplets are hit by the fan-shaped blades of the cooling plate 1 and collide with the inner wall of the cooling chamber 2 to form plate-shaped sheets. However, due to the cooling effect of the liquid nitrogen in the cooling jacket 2, no recovery or recrystallization occurs.

[0013] Step 4: Hot-press and sinter the two metal layers in a hot-pressing chamber 3 at a temperature of 600°C and a pressure of 800-1000 MPa for 30 minutes. During this process, the morphologies of the Ti and Al metals are restored, causing the Al metal to soften and wrap around the Ti metal.

[0014] Step 5: Repeat step 2 to lay the Ti powder in the hot pressing chamber 3;

[0015] Step 6: Repeat step 3 twice to lay Mg powder and Al powder in the hot pressing chamber 3 respectively;

[0016] Step 7: Hot press sintering the entire laminate in the hot press chamber 3 at a temperature of 600°C and a pressure of 800-1000 MPa for 30 minutes. During this process, the morphologies of the Ti, Mg, and Al metals are restored, causing the Al and Mg metals to soften and wrap around the Ti metal.

[0017] Step 8: Repeat step 2 to lay the Ti powder in the hot pressing chamber 3;

[0018] Step 9: Repeat step 3 three times to lay Mg powder, Cu powder, and Al powder in the hot pressing chamber 3 respectively;

[0019] Step 10: Repeat step 2 to lay Ti powder in the hot pressing chamber 3;

[0020] Step 11: Hot press sintering is performed on the entire laminate in the hot pressing chamber 3 at a sintering temperature of 600°C and a pressure of 800-1000 MPa for 30 minutes. The temperature is then increased to 1000-1100°C and the pressure is increased to 1500-1700 MPa for 30 minutes. After cooling to room temperature, a powder block material with high strength and cohesive microstructure can be obtained.

[0021] In this embodiment, Ti and Al serve as matrix materials, and Mg and Cu serve as strengthening agents. During the low-temperature sintering stage, Al and Mg are softened and wrapped around Ti, so that Ti always maintains a certain "boundary", while Cu does not melt during the sintering stage and always maintains a plate shape, embedded in the microstructure. During the high-temperature sintering stage, Al and Mg melt on the one hand, filling the microstructure gaps like "mortar", while Cu is only slightly melted, and the internal strength is improved with the help of surface tension.

[0022] The prepared Mg-Al-Ti-Cu compound is a bulk material, which is mainly composed of Ti, Al, Mg and Cu. The components in the microstructure have different forms. Ti is nearly spherical and wrapped with Al and Mg. Cu is plate-like, small in size and embedded in Ti, Al and Mg, and dispersed in the microstructure. This microstructure is similar to a "brick and mortar" design, achieving high strength and high cohesion of the microstructure and inhibiting crack propagation. In addition, before hot pressing and sintering of the powder metallurgy material, the Ti, Al, Mg and Cu powders appear in the microstructure in the form of particles and plates, respectively. The particles and plates before hot pressing are full of defects such as dislocations. These defects make it easier to refine the grains during the subsequent hot pressing and sintering process, increasing the overall strength of the material by 30%.

[0023] In this implementation device, through the design of the cooling plate and cooling chamber, the powder raw material can quickly change its shape while freezing the internal defects of the powder. By utilizing the heat-resistant properties of Ti, Al, Mg and Cu, a thin-sheet intercalated microstructure is formed during the subsequent heat treatment process, thereby blocking dislocation movement and improving the alloy's stress resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a structural diagram of the device described in the technical solution of the present invention DETAILED DESCRIPTION

[0025] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments:

[0026] See attached Figure 1As shown, the apparatus for implementing the method of the present invention includes a cooling plate 1, a cooling jacket 2, and a hot pressing chamber 3. The cooling plate 1 is capable of rotating about its central axis and has fan-shaped blades installed on its edge. The fan-shaped blades are distributed radially along the circumference of the rotation of the cooling plate 1. The cooling jacket 2 containing liquid nitrogen is arranged around the cooling plate 1, and the hot pressing chamber 3 is arranged below the cooling jacket 2. The cooling jacket 2 and hot pressing chamber 3 are made of stainless steel.

[0027] In this embodiment, the Mg-Al-Ti-Cu compound is prepared using the above-mentioned device, and the steps are as follows:

[0028] Step 1: Prepare Mg powder, Al powder, Ti powder and Cu powder with a particle size of -300 to -400 mesh, wherein the volume percentages of Mg powder and Cu powder are 20% and 10% respectively, and the volume percentages of Ti powder and Al powder are both 35%;

[0029] Step 2: Start the cooling plate 1 and rotate it at a speed of 50-200 rad / s. Sprinkle Ti powder from the top of the cooling plate 1, allowing the Ti powder to pass through the cooling plate 1 and the cooling chamber 2 into the hot pressing chamber 3 to form a layer. During this process, the Ti powder is hit by the fan-shaped blades of the cooling plate 1 and collides with the inner wall of the cooling chamber 2, causing plastic deformation. However, due to the cooling effect of the liquid nitrogen in the cooling jacket 2, recovery and recrystallization do not occur.

[0030] Step 3: The molten Al powder droplets are passed through the cooling plate 1 and the cooling chamber 2 into the hot pressing chamber 3 to form a layer. During this process, the aluminum powder droplets are hit by the fan-shaped blades of the cooling plate 1 and collide with the inner wall of the cooling chamber 2 to form plate-shaped sheets. However, due to the cooling effect of the liquid nitrogen in the cooling jacket 2, no recovery or recrystallization occurs.

[0031] Step 4: Hot-press and sinter the two metal layers in a hot-pressing chamber 3 at a temperature of 600°C and a pressure of 800-1000 MPa for 30 minutes. During this process, the morphologies of the Ti and Al metals are restored, causing the Al metal to soften and wrap around the Ti metal.

[0032] Step 5: Repeat step 2 to lay the Ti powder in the hot pressing chamber 3;

[0033] Step 6: Repeat step 3 twice to lay Mg powder and Al powder in the hot pressing chamber 3 respectively;

[0034] Step 7: Hot press sintering the entire laminate in the hot press chamber 3 at a temperature of 600°C and a pressure of 800-1000 MPa for 30 minutes. During this process, the morphologies of the Ti, Mg, and Al metals are restored, causing the Al and Mg metals to soften and wrap around the Ti metal.

[0035] Step 8: Repeat step 2 to lay the Ti powder in the hot pressing chamber 3;

[0036] Step 9: Repeat step 3 three times to lay Mg powder, Cu powder, and Al powder in the hot pressing chamber 3 respectively;

[0037] Step 10: Repeat step 2 to lay Ti powder in the hot pressing chamber 3;

[0038] Step 11: Hot press sintering is performed on the entire laminate in the hot pressing chamber 3 at a sintering temperature of 600°C and a pressure of 800-1000 MPa for 30 minutes. The temperature is then increased to 1000-1100°C and the pressure is increased to 1500-1700 MPa for 30 minutes. After cooling to room temperature, a powder block material with high strength and cohesive microstructure can be obtained.

Claims

1. A powder metallurgy method for improving strength and obtaining a cohesive microstructure, characterized by: The device used in the metallurgical method includes a cooling plate (1), a cooling jacket (2) and a hot pressing chamber (3); the cooling plate (1) is capable of rotating around its central axis and has fan-shaped blades installed on its edge; a cooling jacket (2) containing liquid nitrogen is arranged around the cooling plate (1); and a hot pressing chamber (3) is arranged below the cooling jacket (2); The steps of preparing Mg-Al-Ti-Cu compound using the device are as follows: Step 1: Prepare Mg powder, Al powder, Ti powder and Cu powder with a particle size of -300~-400 mesh, wherein the volume percentage of Mg powder and Cu powder is 20% and 10% respectively, and the volume percentage of Ti powder and Al powder is 35%; Step 2: Start the cooling disk (1) at a rotation speed of 50-200 rad / s, sprinkle Ti powder from the top of the cooling disk (1), and allow the Ti powder to pass through the cooling disk (1) and the cooling jacket (2) into the hot pressing chamber (3) to form a layer. During this process, the Ti powder is hit by the fan-shaped blades of the cooling disk (1) and collides with the inner wall of the cooling jacket (2) to cause plastic deformation, but due to the cooling effect of the liquid nitrogen in the cooling jacket (2), no recovery or recrystallization occurs; Step 3: The molten Al powder droplets are passed through the cooling plate (1) and the cooling jacket (2) into the hot pressing chamber (3) to form a layer. During this process, the aluminum powder droplets are hit by the fan-shaped blades of the cooling plate (1) and collide with the inner wall of the cooling jacket (2) to form a plate shape. However, due to the cooling effect of the liquid nitrogen in the cooling jacket (2), recovery and recrystallization do not occur. Step 4: hot-pressing and sintering the two metal layers in a hot-pressing chamber (3) at a sintering temperature of 600°C and a pressure of 800-1000 MPa for 30 minutes. During this process, the Al metal softens and wraps the Ti metal. Step 5: Repeat step 2 to lay the Ti powder in the hot pressing chamber (3); Step 6: Repeat step 3 twice to lay Mg powder and Al powder in the hot pressing chamber (3) respectively; Step 7: hot pressing and sintering the entire laminate in the hot pressing chamber (3) at a sintering temperature of 600°C and a pressure of 800-1000 MPa for 30 minutes. During this process, the Al metal and the Mg metal are softened and wrap around the Ti metal. Step 8: Repeat step 2 to lay Ti powder in the hot pressing chamber (3); Step 9: Repeat step 3 three times to lay Mg powder, Cu powder and Al powder in the hot pressing chamber (3) respectively; Step 10: Repeat step 2 to lay Ti powder in the hot pressing chamber (3); Step 11: hot press sintering the entire laminate in the hot press chamber (3) at a sintering temperature of 600°C and a pressure of 800-1000 MPa for 30 minutes, then raising the temperature to 1000-1100°C and the pressure to 1500-1700 MPa for 30 minutes, and cooling to room temperature to obtain a powder block material with high strength and cohesive microstructure.

2. The powder metallurgy method for improving strength and obtaining a cohesive microstructure according to claim 1, characterized in that: The fan-shaped blades are distributed along the radial direction of the rotation circumference of the cooling disk (1).

3. The powder metallurgy method for improving strength and obtaining a cohesive microstructure according to claim 1, characterized in that: The cooling jacket (2) and the hot pressing chamber (3) are made of stainless steel.

Images